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25 Dec 1995

Volume 67, Issue 26, pp. 3835-3983

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Direct measurements of the true vibrational amplitudes in shear force microscopy

Chih‐Chun Wei, Pei‐Kuen Wei, and Wunshain Fann

Appl. Phys. Lett. 67, 3835 (1995); http://dx.doi.org/10.1063/1.115289 (3 pages) | Cited 24 times

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A new method to measure the tip’s true vibrational amplitude in the shear force microscopy is demonstrated. The measurements are based on modifications of the beam diffraction method. In addition to the dither vibration, the equilibrium position of the tip is set to move along the direction of the vibration. The ratio of ac amplitude to the derivative of dc amplitude gives the tip’s vibration. The sensitivity of this method is determined by the size of the laser focal spot times the ratio of the ac to dc signals of the diffracted light. © 1995 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.79.Lh Atomic force microscopes

Effect of beam thickness in a Cherenkov laser

T. Ueda and T. Shiozawa

Appl. Phys. Lett. 67, 3838 (1995); http://dx.doi.org/10.1063/1.115290 (3 pages) | Cited 3 times

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The effect of beam thickness in a two‐dimensional Cherenkov laser is investigated on the basis of the fluid model for the electron beam. In the analysis, the transverse variation of the drift velocity for the electron beam is taken into account. The numerical simulation shows that there exists an optimum beam thickness for an efficient use of the electron beam in the Cherenkov laser. © 1995 American Institute of Physics.
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41.60.Bq Cherenkov radiation
41.60.Cr Free-electron lasers

Broadband pump wavelength tuning of a low threshold N‐(4‐nitrophenyl)‐L prolinol near infrared optical parametric oscillator

S. Khodja, D. Josse, I. D. W. Samuel, and J. Zyss

Appl. Phys. Lett. 67, 3841 (1995); http://dx.doi.org/10.1063/1.115291 (3 pages) | Cited 4 times

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We report the pump wavelength tuning of a low threshold N‐(4‐nitrophenyl)‐L‐prolinol based nanosecond pulsed optical parametric oscillator in the near infrared. A broad tuning range from 1 to 1.5 μm corresponds to a limited pump wavelength excursion from 583 to 590 nm and a record low oscillation threshold of the order of 0.5 MW cm−2. © 1995 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Terahertz photomixing with diode lasers in low‐temperature‐grown GaAs

K. A. McIntosh, E. R. Brown, K. B. Nichols, O. B. McMahon, W. F. DiNatale, and T. M. Lyszczarz

Appl. Phys. Lett. 67, 3844 (1995); http://dx.doi.org/10.1063/1.115292 (3 pages) | Cited 119 times

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Recent optical heterodyne measurements with distributed‐Bragg‐reflector diode‐laser pumps demonstrate that low‐temperature‐grown (LTG) GaAs photomixers will be useful in a compact all‐solid‐state terahertz source. Electrical 3 dB bandwidths as large as 650 GHz are measured in mixers with low electrode capacitance. These bandwidths appear to be independent of pump‐laser wavelength over the range 780–850 nm. Shorter wavelength pumping results in a significant reduction of the bandwidth. The best LTG‐GaAs photomixers are used to generate coherent continuous‐wave output radiation at frequencies up to 5 THz. © 1995 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters

Metallization to asymmetric cladding separate confinement heterostructure lasers

G. M. Smith, D. V. Forbes, R. M. Lammert, and J. J. Coleman

Appl. Phys. Lett. 67, 3847 (1995); http://dx.doi.org/10.1063/1.115293 (3 pages) | Cited 16 times

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Annealed and nonannealed p‐contact metallization for asymmetric cladding separate confinement heterostructure lasers with a thin p‐cladding layer is reported. Ti–Au and annealed Ti–Pt–Au p‐type contacts are demonstrated to improve the adhesion over a pure gold contact and allow annealing of the metallization to thin p‐cladding laser structures at the expense of an increase in the optical loss. The increased optical loss is due to the decreased conductivity of titanium and platinum as compared to gold. As little as 10 Å of titanium is adequate for an adhesion layer and only increases the optical loss by 1.6 cm −1 over a pure gold metallization which has an optical loss of 10.0 cm−1. A metallization of 15 Å Ti−15 Å Pt−1500 Å Au is adequate for an anneal at 410 °C for 10 s and increases the optical loss by 7.0 cm −1. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Enhanced nonlinear absorption and optical limiting in semiconducting polymer/methanofullerene charge transfer films

M. Cha, N. S. Sariciftci, A. J. Heeger, J. C. Hummelen, and F. Wudl

Appl. Phys. Lett. 67, 3850 (1995); http://dx.doi.org/10.1063/1.115294 (3 pages) | Cited 48 times

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Nonlinear optical absorption in solid films of poly(3‐octylthiophene) (P3OT) sensitized with methanofullerene was investigated for wavelengths from 620 to 960 nm. The nonlinear absorption is enhanced over that in either of the component materials by more than two orders of magnitude at 760 nm. The large nonlinearity results from efficient photoinduced intermolecular charge transfer from P3OT to methanofullerene, followed by absorption in the charge separated excited state. P3OT/fullerene films are promising as optical limiters; the transmission clamps at an average fluence of approximately 0.1 J/cm2. The damage threshold was 15 μJ/pulse (≊1 J/cm2 in average fluence), above which there is a permanent change in the linear transmission. © 1995 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Qn Polymers; organic compounds

Highly efficient blue electroluminescence from a distyrylarylene emitting layer with a new dopant

Chishio Hosokawa, Hisahiro Higashi, Hiroaki Nakamura, and Tadashi Kusumoto

Appl. Phys. Lett. 67, 3853 (1995); http://dx.doi.org/10.1063/1.115295 (3 pages) | Cited 265 times

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We report that organic electroluminescence devices with a distyrylarylene (DSA) emitting layer including a new dopant realized highly efficient and bright emission in blue region. This dopant was amino‐substituted DSA. The luminous efficiency was obtained to be 1.5 lm/W. The external quantum efficiency was estimated to be 2.4%, which is one of the highest efficiencies ever reported in blue emitting organic EL devices. © 1996 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds
85.60.Jb Light-emitting devices

Self‐induced phase gratings due to the inhomogeneous structure of acrylamide photopolymer systems used as holographic recording materials

A. Beléndez, A. Fimia, L. Carretero, and F. Mateos

Appl. Phys. Lett. 67, 3856 (1995); http://dx.doi.org/10.1063/1.115296 (3 pages) | Cited 9 times

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We report the observation of self‐induced gratings or noise gratings in an acrylamide photopolymer for use in real time holography. The possibilities of this noise source as an optimization technique for this type of material are pointed out. Noise gratings in these polymer films were created upon exposure to a He–Ne laser collimated beam at 633 nm without any subsequent processing step. The influence of intensity on recording noise gratings and angular selectivity are reported showing its influence on the recording of this type of noise source in real time holographic materials. © 1995 American Institute of Physics.
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42.40.-i Holography
42.70.Ln Holographic recording materials; optical storage media

Near‐field direct‐write ultraviolet lithography and shear force microscopic studies of the lithographic process

Igor I. Smolyaninov, David L. Mazzoni, and Christopher C. Davis

Appl. Phys. Lett. 67, 3859 (1995); http://dx.doi.org/10.1063/1.115297 (3 pages) | Cited 53 times

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Direct‐write lithography on a 100 nm scale has been carried out using the near‐field optical interaction between an uncoated tapered fiber tip and a layer of photoresist. This allows both lithography and shear force microscopic examination of the surface, which reveals morphological changes in the photoresist before development. © 1995 American Institute of Physics.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer

Transmission electron microscopy of 〈100〉 dark line defects in CdZnSe quantum well structures

G. D. U’Ren, G. M. Haugen, P. F. Baude, M. A. Haase, K. K. Law, T. J. Miller, and B. J. Wu

Appl. Phys. Lett. 67, 3862 (1995); http://dx.doi.org/10.1063/1.115298 (3 pages) | Cited 7 times

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The initial degradation of II–VI light emitting devices, namely the 〈100〉 dark line defect formation in CdZnSe quantum well structures formed during laser or light emitting diode (LED) operation, has been investigated. Optically degraded quantum well structures exhibiting dark line defects were investigated via transmission electron microscopy. The observable dislocation networks have been determined to be conglomerations of dislocation loops confined to the quantum well region having an associated Burgers vectors of a[100] and a[010]. The discovery and identification of initial dark line defects may prove useful in identifying the defect mechanism in II–VI light emitters. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
85.60.Jb Light-emitting devices

Spatial and spectral characteristics of spontaneous emission from semiconductor quantum wells in microscopic cylindrical cavities

Igor Vurgaftman and Jasprit Singh

Appl. Phys. Lett. 67, 3865 (1995); http://dx.doi.org/10.1063/1.115299 (3 pages) | Cited 4 times

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The spontaneous emission rate from an In0.2Ga0.8As quantum well in a cylindrical dielectric cavity with submicron radii and without mirrors in the emission plane is calculated based on a rigorous description of the cavity modes and their interaction with the 2D electronic system. The rate is suppressed for radii much less than the peak optical wavelength (rcav≪λ/n), enhanced by up to a factor of ≊8 for rcav≊λ/n, and remains similar to its value in the absence of a cavity for rcav≫λ/n. The emitted light produces a highly collimated vertical beam in the intermediate region with the majority of photons emitted into the guided cavity modes, and its spatial distribution broadens dramatically in the smallest structures. The global spectral width of spontaneous emission in cavities that can presently be fabricated is largely unaffected by the introduction of lateral dielectric boundaries. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Three‐terminal laser structure for high‐speed modulation using dynamic carrier heating

Valery I. Tolstikhin and Marco Mastrapasqua

Appl. Phys. Lett. 67, 3868 (1995); http://dx.doi.org/10.1063/1.115300 (3 pages) | Cited 1 time

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A three‐terminal laser structure is proposed as a means to achieve laser modulation using dynamic carrier heating. The injection of hot electrons, with energy tuned by variable joule heating over a high electric field region, is used to govern the carrier temperature in the active layer of a laser, while a separate heterojunction controls the injection rate. Simulations show the possibility of generating good‐shaped picosecond optical pulses by modulating the voltage that controls the heating electric field. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Z‐scan studies and optical limiting in a mode‐locking dye

G. Ravindra Kumar and F. A. Rajgara

Appl. Phys. Lett. 67, 3871 (1995); http://dx.doi.org/10.1063/1.115301 (3 pages) | Cited 7 times

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The optical nonlinearity of a mode‐locking dye (Kodak 9740) under picosecond excitation at 532 nm, is studied using the Z‐scan technique. Theoretical fits to the data give a value of 3.2 cm/GW for the two‐photon absorption coefficient (β) and −2.1×10−5 cm2/GW for the real part (γ) of the nonlinearity. In addition, we demonstrate optical limiting using two‐photon absorption as well as self‐defocusing. © 1995 American Institute of Physics.
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42.65.-k Nonlinear optics
42.70.Jk Polymers and organics

Polymeric electro‐optic Mach–Zehnder switches

J. I. Thackara, J. C. Chon, G. C. Bjorklund, W. Volksen, and D. M. Burland

Appl. Phys. Lett. 67, 3874 (1995); http://dx.doi.org/10.1063/1.115302 (3 pages) | Cited 17 times

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Polymeric 2×2 electro‐optic switches based on the balanced bridge, or Mach–Zehnder, design are presented. Two poled nonlinear optical side‐chain polymers based on the dye Disperse Red 1, one with a glass transition temperature Tg of 131 °C and the other with a Tg of 228 °C, were used as the active layers in these devices. The switch designs incorporated traveling‐wave electrodes in the phase shift sections and, for the lower Tg polymer device, electrically adjustable 3 dB couplers. At the 1.32 μm operating wavelength, extinction ratios of at least 28 dB were achieved in all four states of the lower Tg switch with a propagation loss of 1.6 dB/cm and a small signal 3 dB modulation bandwidth of over 2 GHz. © 1995 American Institute of Physics.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Pulse‐shaping mechanism in colliding‐pulse mode‐locked laser diodes

S. Bischoff, M. P. Sørensen, J. Mørk, S. D. Brorson, T. Franck, J. M. Nielsen, and A. Møller‐Larsen

Appl. Phys. Lett. 67, 3877 (1995); http://dx.doi.org/10.1063/1.115303 (3 pages) | Cited 17 times

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The large signal dynamics of passively colliding pulse mode‐locked laser diodes is studied. We derive a model which explains modelocking via the interplay of gain and loss dynamics; no bandwidth limiting element is necessary for pulse formation. It is found necessary to have both fast and slow absorber dynamics to achieve mode‐locking. Significant chirp is predicted for pulses emitted from long lasers, in agreement with experiment. The pulse width shows a strong dependence on both cavity and saturable absorber length. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Discharge frequency dependence of particulate growth in high frequency silane plasmas

H. Kawasaki, Y. Ueda, T. Yoshioka, T. Fukuzawa, M. Shiratani, and Y. Watanabe

Appl. Phys. Lett. 67, 3880 (1995); http://dx.doi.org/10.1063/1.115304 (3 pages) | Cited 4 times

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Discharge frequency dependence of growth of particulates is studied in high frequency silane plasmas. Particulates appear earlier after discharge initiation and the increasing rate of their amount in the subsequent phase decreases with increasing the discharge frequency from 3.5 to 28 MHz. Even in the early phase of their formation for all 3.5–28 MHz discharges, particulates grow principally around the plasma/sheath boundary near the powered electrode, where short lifetime radicals are actively generated. For 28 MHz, the density of particulates in the early discharge phase is extremely high (≥1011 cm3). The latter two features suggest that many short lifetime neutral radicals (such as SiH2), being produced at a high rate, significantly contribute to the nucleation and initial growth of one particulate, at least, for a relatively high power density of the order of 0.5 W/cm2. © 1995 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.80.Pi High-frequency and RF discharges
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Luminescence properties of submicron features fabricated by using magnetron reactive ion etching with different sample biases

M. Freiler, G. F. McLane, S. Kim, M. Levy, R. Scarmozzino, I. P. Herman, and R. M. Osgood

Appl. Phys. Lett. 67, 3883 (1995); http://dx.doi.org/10.1063/1.115305 (3 pages) | Cited 4 times

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Deep‐etch‐defined GaAs/Al0.3Ga0.7As square features of multiquantum well material, with dimensions as small as 160 nm, have been fabricated using magnetron reactive ion etching (MIE). Luminescence spectroscopy shows confinement of charge carriers to the features’ center. The effects of rf power and etching time on the luminescence efficiency of these features and its concomitant etch‐induced damage are examined. © 1995 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.55.Cr III-V semiconductors
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer

Importance of channeled implantation to the synthesis of erbium silicide layers

M. F. Wu, A. Vantomme, H. Pattyn, and G. Langouche

Appl. Phys. Lett. 67, 3886 (1995); http://dx.doi.org/10.1063/1.115306 (3 pages) | Cited 12 times

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166Er atoms were implanted with an energy of 70 to 90 keV and doses of 0.8 to 2.0×1017/cm2 into Si(111) substrates at temperatures ranging from 450 to 530 °C. We found that using conventional nonchanneled implantation at energies of ∼90 keV, it is impossible to form a continuous ErSi1.7 layer. At best, after annealing, a discontinuous ErSi1.7 layer with poor crystalline quality (χmin=40%) is obtained. On the contrary, using channeled implantation, a continuous epitaxial ErSi1.7 layer with very good crystalline quality can be formed; a lowest χmin value of 1.5% for a surface ErSi1.7 layer has been obtained. The origin of this different behavior is explained. Our results show that for synthesizing continuous ErSi1.7 layers with good quality using ion beam synthesis at energies around 90 keV, channeled implantation is indispensable. © 1995 American Institute of Physics.
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61.80.Jh Ion radiation effects
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Total reflection x‐ray excited photoelectron spectra of copper phthalocyanine thin layer on Si wafer

Jun Kawai, Shin’ichi Kawato, Kouichi Hayashi, Toshihisa Horiuchi, Kazumi Matsushige, and Yoshinori Kitajima

Appl. Phys. Lett. 67, 3889 (1995); http://dx.doi.org/10.1063/1.115307 (3 pages) | Cited 8 times

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Photoelectron spectra of a Si wafer, on which copper phthalocyanine was evaporated with a thickness of 50 Å, were measured using grazing incidence x rays under a total reflection condition. It was observed that the backgrounds owing to inelastic electron scattering in solids were reduced. It was also observed that the substrate Si signal was removed and that surface signal was enhanced due to the total x‐ray reflection. Oxygen depth was determined using the angle dependence of the x‐ray photoelectron spectral intensity. © 1995 American Institute of Physics.
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79.60.Dp Adsorbed layers and thin films
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Photoacoustic procedure for measuring thermal parameters of transparent solids

W. L. Barros Melo and R. M. Faria

Appl. Phys. Lett. 67, 3892 (1995); http://dx.doi.org/10.1063/1.115308 (3 pages) | Cited 11 times

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An application of photoacoustic technique is developed for determining the thermal diffusivity coefficient and the thermal conductivity of transparent materials. The backing material which supports the sample is made optically opaque, i.e., it entirely absorbs the incident light, and the converted heat diffuses through the sample heating the gas in contact with its opposite surface. The method is illustrated by fitting voltage amplitude and phase signals versus the chopping frequency in the photoacoustic cell, according to a theoretical model of heat diffusion. Thermal parameters obtained for three polymers compare very well with results from the literature. © 1995 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Electro‐optical characteristics and switching behavior of the in‐plane switching mode

Masahito Oh‐e and Katsumi Kondo

Appl. Phys. Lett. 67, 3895 (1995); http://dx.doi.org/10.1063/1.115309 (3 pages) | Cited 263 times

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Electro‐optical characteristics related to the threshold behavior of liquid crystals when using the in‐plane switching (IPS) mode were investigated with interdigital electrodes. In order to analyze the switching behavior of liquid crystals, an equation, which expresses the threshold transition, was derived using the continuum elastic theory. It was made clear that it was the electric field and not the voltage that drives the liquid crystals in the IPS mode. Significantly, an inversely proportional relationship between the threshold voltage and the gap between the substrates was found to hold. Furthermore, the electro‐optical characteristics were recognized to change with the variation of the gap between the substrates. This behavior is due to the independence of electric field on liquid crystal layer normal. © 1995 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Diamond nucleation by seeding from the gas phase

Z. Ajji, M. Buck, and Ch. Wöll

Appl. Phys. Lett. 67, 3898 (1995); http://dx.doi.org/10.1063/1.115310 (3 pages)

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In a hot‐filament reactor diamond films were deposited on various substrates without pretreatment. A nickel wire placed at a short distance above the substrate yields an increase of the nucleation density by five orders of magnitude. Closed diamond films were obtained for different substrate materials. The deposits were characterized by scanning electron microscopy, Raman spectroscopy, and x‐ray photoelectron spectroscopy. The presence of Ni in the diamond films indicates that Ni containing species are transported through the gas phase during the reaction to the substrate surface thus forming nucleation centers. Replacing the Ni wire by a diamond membrane nucleation enhancement is reduced by about three orders of magnitude. The pronounced distance dependence observed suggests that volatile unstable species are produced which form nucleation centers upon impact on the substrate surface. © 1995 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Growth and interfacial evolution of oriented C60 overlayers on Au(111)

A. Fartash

Appl. Phys. Lett. 67, 3901 (1995); http://dx.doi.org/10.1063/1.115311 (3 pages) | Cited 4 times

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High‐quality C60(111) overlayers are grown on Au(111)/Ag(111)/mica substrates and their structures studied by x‐ray diffraction. The structural evolution of these overlayers is investigated for growth temperatures from 120 to 290 °C. C60(111) overlayers undergo an in‐plane orientational reordering at To∼150 °C. Above this temperature, the rotated and commensurate in‐plane structures coexist with each other. The rotated structures evolve from the in‐plane structures, which predominate at temperatures below To. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology

Work function and desorption energy of H− from heated CaH2

Hiroyuki Kawano, Naoshi Serizawa, and Makiko Takeda

Appl. Phys. Lett. 67, 3904 (1995); http://dx.doi.org/10.1063/1.115312 (2 pages) | Cited 9 times

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A powdery sample of CaH2 heated to ∼730–790 K in a readily attainable high vacuum (∼1 ×10−7 Torr) was found to emit thermal electrons (∼ 10−7–10−5 A) and H− ions (∼ 10−15–10−12 A, mass analyzed) from its surface (∼ 0.1 cm2). The work function of the sample and the desorption energy of H− were 4.8 ± 0.1 and 7.4 ± 0.2 eV, respectively. The latter fairly agreed with the value (7.1 ± 0.1 eV) derived theoretically by our simple model for the thermal negative ion emission. © 1995 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
79.40.+z Thermionic emission
79.70.+q Field emission, ionization, evaporation, and desorption

Novel laser gain media based on Cr3+‐doped mixed borates RX3(BO3)4

Guofu Wang, T. P. J. Han, H. G. Gallagher, and B. Henderson

Appl. Phys. Lett. 67, 3906 (1995); http://dx.doi.org/10.1063/1.115313 (3 pages) | Cited 15 times

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This letter discusses the optical properties of Cr3+ ions in mixed borate crystals with the formula RX3(BO3)4, where R3+=Y3+ or Gd3+ and X3+=Al3+ or Sc3+. Measurements of the optical absorption spectra have been used to estimate the crystal field strength Dq and the Racah parameters B and C. These quantities confirm that in YAl3(BO3)4(YAB) and GdAl3(BO3)4(GAB)Cr3+ ions occupy strong crystal field sites 2E)<E(4T2)], whereas in YSc3(BO3)4(YSB) and GdSc3(BO3)4(GSB) the Cr3+ ions occupy weak field sites 4T2)<E(2E)]. The consequence is that the fluorescence spectrum of Cr3+:YAB and GAB reveals the sharp R lines at low temperature and R lines plus broadband at 300 K. Both Cr3+:YSB and GSB emit into the broadband 4T2→4A2 transition at all temperatures. The potential of these materials as laser gain media is discussed. © 1995 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
71.55.Ht Other nonmetals
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